As a heat treatment carried out during a product manufacturing process, there are known a heat treatment carried out to improve toughness or the like by changing a structure of a product and also a heat treatment carried out to remove any unrequired material applied to the product. An example of the unrequired material is a masking used in performing a coating or the like to a surface of the product, and the masking is decomposed or burned to be removed therefrom by performing an ashing process, which is an example of the heat treatment (see Patent Document 1).
PATENT DOCUMENT 1: Japanese Unexamined Patent Application, First Publication No. 2001-173405 (Page 7)